Differential Sedimentation and Cryo-TEM Mapping Resolve Structural Heterogeneity in Conjugated Polymer Nanowires for Programmable Stretchable Electronics.

The performance of stretchable electronics based on semicrystalline conjugated polymers (CPs) is determined by the balance between crystalline order and interdomain connectivity provided by amorphous tie molecules, rather than by crystallinity alone. Solution-state crystallization-driven self-assembly (CDSA) of CPs into nanowires (NWs) enables solution-processable thin films without post-deposition annealing to enhance crystallinity. In cast films, crystalline NWs provide charge-transport pathways, whereas non-aggregated amorphous chains bridge adjacent NW crystallites, sustain interdomain charge percolation, and accommodate mechanical deformation. Yet this assembly inevitably yields heterogeneous mixtures of crystalline NWs and amorphous chains, which resist single-NW quantification and independent control. In this study, density-driven differential sedimentation fractionates poly(3-hexylthiophene) (P3HT) NWs into a sediment of crystalline NWs and a supernatant of shorter NWs and lower-molecular-weight chains. Cryo-TEM quantitative morphological mapping resolves backbone tilt, width uniformity, and lamellar coherence at the single-NW level, showing that local cofacial π-π packing is preserved in both fractions whereas long-range order along the lamellar stacking direction is concentrated in the sediment. Recombining the fractions at controlled weight ratios tunes the mobility-stretchability trade-off without chemical modification, and the strategy generalizes to coaxial p-n heterojunction hybrid NWs of P3HT-b-poly(2-vinylpyridine)/CdSe quantum dots formed by CDSA, reframing structural heterogeneity as a programmable design parameter for stretchable electronics.